Modern dental practices, whether associated with restoration or prophylaxis, involve both the influx of water and air into the patient's oral cavity as well as the ejection or removal of saliva and debris. While in prior years little attention was devoted to ensuring biologically pure water and air supplies, the reverse is now true, particularly in view of concerns with transmission of infectious diseases such as hepatitis and HIV, as well as concerns relative to previously unrecognized general systemic infection (sepsis) which may result when infectious agents encounter cut or abraded oral tissue.
Although heightened hygiene in dental work has fostered the wide-spread use of rubber gloves, face masks, and high temperature sterilization of dental implements, the air and water supplies, both of which are prime conduits for infectious agents, have received little attention. Compressed air supplies, for example, have been conditioned by traditional filter elements containing fibrous material, for example cotton or fiber glass. While such filters are effective to remove oil mist from compressors, dust, and other particulate matter of large dimension, they are of little effectiveness with regard to microbes such as bacteria, yeasts, fungi, and viruses. Moreover, the microbes which may be initially removed may reproduce in the filter elements themselves, ultimately contributing to microbe contaminated air.
Water supplies have also been traditionally filtered, either by fibrous or wound filters or by beds of activated carbon, zeolites, alumina, etc. Such beds and filters are notorious for harboring microbes, however, and thus such filters, while being effective to remove major particulates, and, in the case of activated carbon, organic contaminants, have only marginal effectiveness with respect to microorganisms, with even this marginal effectiveness being of short duration.
In U.S. Pat. No. 4,950,159 is disclosed a filter element for a dental syringe in which a longitudinal filter element divided into two compartments filters the water and air supplies just prior to dispersal from the syringe. However, the filtration elements are activated charcoal for the water supply and cotton fleece for the air supply. Neither of these filtration elements is well suited to eliminate microbes from the respective supplies. Moreover, the device allows contaminated air and water to be backflushed into the supply systems should a reduction in pressure occur, or even by remaining at static pressure for extended periods. In this manner, infectious agents may be transmitted from patient to patient. As the unit is of high cost, currently in the range of 20-30 dollars, it is not a one-time use disposable filter.
U.S. Pat. No. 5,204,004 discloses a filtration element for the water supply to a dental syringe, employing a microporous membrane. Unfortunately, the air supply is left unfiltered. The element is not readily adapted to the input fittings on many syringes in common use, and must instead be spliced into a split and cut water line. The '004 filtration is thus not a point of use device, nor it is subject to easy and rapid replacement. Finally, its location several inches upstream from the syringe leaves several inches of tubing which may contain a biologically active microbial coating along its interior surface.